Process for electrodepositing iron



PROCESS FOR ELECTRODEPOSITING IRON Filed Dec. 12, 1928 @wiow PatentedJune 14, 1932 UNITED STATES PATENT OFFICE GEORGE PRESCOTT FULLER, OFNIAGARA FALLS, NEW YORK, AND CEDRIC A. VINCENT DAVISS, F NIAGARA FALLS,ONTARIO, CANADA, ASSIGNORS, BY MESNE ASSIGN- MENTS, OF ONE-HALF T0 SAIDFULLER AND ONE-HALF TO EDWARD MICHAEL, 0F

BUFFALO, NEW YORK.

PROCESS FOR ELECTRODEI'OSITING IRON I Application filed December 12,1928. Serial'No. 325,499.

This invention relates to improvements in a process for the electrolyticproduction of iron tubes.

Processes for the production of seamless iron tubes by electrodepositionhave long been known and attempts been made to put such processes intocommercial operation but without success because the cost of productionwas too high.

The object of the present invention is to provide an electrolyticprocess for the pro-- duction of such tubes which is more efficient andeconomical than the processes heretofore employed so that tubes made bythis process can be sold at prices which the market will pay.

The invention consists in the features, steps of operation and detailswhich will first be described in connection with the accompanyingdrawing and then more particularly pointed out.

In the drawing- Figure 1 is a diagrammatic view illustrating in ageneral way a plant suitable for car- 2 rying out the process in acontinuous or cyclic manner.

Figure 2 is a horizontal section of one of the electrolytic tanks;

Figure 3 is a cross section ofthe sameon 3 the line 33 of Figure 1 andFigure 4 is an elevation of one of the semipartitions.

An electrolytic cell A of any suitable character capable of containing asolution of electrolyte from the top of the sides of which cell aresuspended in the electrolyte in the cell, as by hooks, two anodes B, ofgraphite, since that material is a conductor and is also insoluble.These anodes'may be treated with molten sulphur -or other suitableimp-regnating material to prevent disintegration, if desired. Cell A isalso arranged to support within it a cathode'C, which is also used as amandrel on which the iron tube is to be formed.

Cathode C is made of high carbon steel, ground and polished so it willbe true and smooth. This cathode or mandrel is required to rotate at acomparatively high speed during the electroplating operation and it istherefore advantageous to have it balanced and located substantiallycentrally in the cell equidistant from the two anodes B. It is mountedalso to be easily removed and replaced. v

Cell A, which may be of concrete or other suitable material, is providedwith a cover D to protect it from injury, prevent loss of heat andreduce the access of air to the electrolyte therein. The electrolyte isfed to the cell from any suitable supply tank E.

Cell A has one compartment for the mandrel, anodes and electrolyte, thatis, no dia phragm is employed. Also the cell is provided a shortdistance from each end, with semi-partitions F, F. The central portionof each partition is substantially of V-form. When partitions F, F areof concrete, it will be advantageous to have suitably supported ingrooves therein, fittings of wood or other suitable material, which whentheir upper and lower parts are in position, form a circular opening toallow such fittings to act as bearings for supporting the journals G, Gof cathode C. Bearings are thus provided 75 which allow of the cathodebeing easily removed and replaced. Owing to the fact that by thisprocess the necessity for a diaphragm is avoided, all the diflicultiesheretofore encountered in such diaphragms are avoided.

Partitions F, F do not extend the full height of the sides of cell A butare somewhat shorter than such sides in order that the electrolyteflowing through the cell may have a substantially free flow over theirtops and also to temporarily retard its flow at that oint.

Cathode C before being placed in the electrolytic cell is thinly anduniformly coated in any suitable manner with an aqueous suspension ofgraphite or similar material to form a parting coating, that is acoating which when the tube has been formed is interposed between themandrel and the tube and thereby allows the tube to be removed easilyand without the necessity of using heat for that purpose. After thegraphite coating has been applied to the mandrel, a thin coating of ironis then electrode osited upon the graphite coating of the man rel at alow 100 current density. This is done preferably in a separate cell. Themandrel is then mounted in position in the electrolytic cell A, with itsjournals resting in their bearings and substantially equidistant fromthe anodes.

The peripheral speed of the mandrel is controlled by the density ofcurrent used, which it is advantageous to have high for the attainmentof satisfactory results.

Although the preplating of the mandrel with iron at low current densityis a great advantage, it may be dispensed with where the current densityduring the main plating operation is relatively low, that is, where thecurrent is not over 60 amperes per square foot. Such preplating may alsobe dispensed with where a hard mandrel is used.

Such preplating is advantageous, however,

in any case, as it removes differences of potential on the cathodesurface, which cause irregular deposits. These differences of potentialare due to variations in the parting material and to impurities andimperfections in the surface of the cathode.

By preplating at a low current density a homogeneous deposit of iron isobtained. \Vith this it is also advantageous to introduce the cathodethus prepared into the cell, and rotate it for a few moments beforeapplying current, with the result that the slightly acid electrolytedissolves a thin film from the iron coating thus removing any remaininginequality and furnishing a surface free of potential differences. lVhenpotential differences exist at the cathode surface, hydrogen is liableto be deposited which causes gas pits or growths, this action beingaccentuated at high current densities. However, when treated asdescribed, current densities far in excess of those heretofore possiblemay be employed.

The electrolyte of the present process consists of a substantiallysaturated hot solution of a ferrous salt, as ferrous chloride, which ismaintained at a ten'iperature of above 80 C. and must be substantiallyfree of suspended matter, such as oxides of iron, and, as fed to theelectrolytic cell, must be entirely free of ferrous hydroxide. Also, itmust contain a trace of iron in ferric form but not to exceed 0.5 gramper litre. This electrolyte may be made in feed tank E, or outside thesystem and introduced therein as desired.

The electrolyte is caused to circulate in a continuous cycle and at arate which is controlled by the density of the electric currentemployed, but the rate of circulation must be such that the maximumcontent of iron in ferric form in the electrolyte while in theelectrolytic cell does not exceed 2.5%

i of the total iron content.

We have discovered that to obtain an acceptable deposit of the iron, itis essential that a trace of ferric chloride be left in the as ferriciron. This prevents the formation of ferrous hydroxide, which we havefound to be very objectionable when working for the production ofperfect commercial seamless tubing, as such ferrous-hydroxide has atendency to cause a deposit of hydrogen on the cathode. The chiefobjection to the ferrous hydroxide is that it forms gas pits or growths,leading to a resulting irregular deposit of the iron.

While it is practicable to remove this objectionable ferrous hydroxideeither by oxidation or filtration, we have found that the oxidationtreatmentcauses complications in the process and also it is diflicult toregulate such treatment. In treatment by filtration also, ferroushydroxide may be formed by hydrolysis after filtering if the solution iscompletely neutral.

In our process neutralization conditions are so regulated that theformation of this objectionable ferrous hydroxide is prevented and,furthermore, we have found that the deposit of the iron on the mandrelis irregular when the ferric iron in the electrolyte exceeds 2.5% of thetotal iron. Excess of ferric iron is prevented by adjusting the rate ofcirculation so that the effluent electrolyte is kept at or below 2.5% ofthe total iron content.

In neutralization it is therefore desirable to reduce the ferric iron tothe lowest possible pOintwithout reaching neutrality, as the more ferriciron is contained in the electrolyte, the more rapid must be thecirculation in order to remove it before the high limit has beenreached.

Since it is desirable that suspend-ed matter in the electrolyte be keptat a minimum, it is usual to employ filtration to this end. In thepresent process, however, such sus pended matter is satisfactorily takencare of ordinarily by settling, thereby dispensing with the necessity ofspecial filtration.

In existing processes suspended matter is derived from the anodes, fromthe iron in the neutralizers, or from hydrolysis of thesolution. In thepresent process, however, through the use of insoluble anodes thatsource is eliminated and the effect of hydrolysis is minimized, thuslimiting the possibility of suspended matter to but one source, namely,the iron in the neutralizers or leaching tanks H, H.

The leaching tanks H and H are filled with iron in metallic form.Although it is most advantageous to use scrap iron for this purpose, itmay be from other suitable sources as ore, or iron in metallic form inother combinations soluble in ferric chloride; or it may be soluble ironfrom any other source which will neutralize the acidity of the effluentelectrolyte. It is in these tanks that the heat is adjusted, that is,the heating coils are arranged to restore the electrolyte to thenecessary C. or over. Another function of these leaching tanks is therestoring to proper concentration of the iron which was removed in thecell before it is-returned to the electrolyte feed tank E by leachingthrough the iron therein.

These tanks may be heated from any suitable source of supply, as from asteam boiler, through steam coils J suitably arranged in the tanks forthat purpose. The leaching tanks H, H and feed or supply tank E are eachprovided with a draw-oil pipe and equipped with ayalve to allow sedimentto be drawn off when necessary. This sediment may then be treated forrecovering anyvaluable contents, if desired.

The efliuent or spent electrolyte is caused.

to circulate through tanks H, H. It will be found advantageous in orderto ensure its being restored to normal, that the electrolyte be causedto flow through both tanks H and H, as shown, after having been used in,and discharged from, the electrolytic cell A, either directly'orindirectly. If but one cell be used, the electrolyte will be dischargedfrom supply tank E into cell A, but if more than one cell be used, as isusual in commercial apparatus, the electrolyte will, for betterdistribution, be through trough I. The

spent electrolyte may also be distributed.

through a trough J and pipe K into the bottom of tank H, thence upwardin tank H and out through the overflow pipe L from the upper end of tankH into the bottom of tank H. From this tank H the electrolyte isWithdrawn by a pump of any suitable character, as the rotary pump Mshown, and pumped back into electrolyte supply or feed tank E ready forre-useand completing the cycle.

The electric current required may be provided by any suitable source ofdirect electric current, the negative terminal R forming the cathodeconnection and the positive collector R forming the connection for theanodes.

While any suitable source of power to rotate the cathode may beemployed, that used for illustration herein has been found satis-*factory. It consists of a shaft 0 driven by a motor 0' directlyconnected thereto inany suitable manner. Shaft O is in turn secured tothe journal of -cathode or mandrel C at a point outside of cell A bysplit coupling P.

An example of a typical run of the process is as follows: N

A concentration of 240 grams per litre of iron in the form of ferrouschloride was used with 0.5 gram per litre as ferric chloride, atemperature of 82 C. being maintained. The peripheral speed of thecathode was 520 feet per minute and the rate of flow of the electrolytewas 9 gallons per minute per square foot of cathode surface. A currentdensity of 125 amperes per square foot was employed, the electrolytefrom the cell being maintained at 4 grams per litre of iron in ferricform. Scrap iron was used to neutralize the solution, and no filtrationwas employed.

This process enables the production of perfect commercial tubes at lowcost through the use of cheap raw material. Control of the deposit isattained through the employment of very high current densities, with ahigher proportion of good deposits, and a lower content of impurities,especially car bon, in the resulting iron. In addition, the process isvery simple.

What is claimed is:

1. The process of electro-depositing seamless iron tubes on a rotatablecathode located in a one-compartment electrolytic cell pro vided withinsoluble anodes, which consists in iron compound soluble in ferric saltso that the ferric iron shall not exceed .5 gram per litre, andreturning the electrolyte to the cell.

2. The process of producing seamless iron tubes consisting incontinuously circulating a substantially saturated hot solution offerrous salt containing a trace of ferric salt in an electrolytic cellin which is rotatably and removably mounted between insoluble anodes acathode capacitated to currents of high density, controlling the rate ofcirculation in proportion to the density of the current so that theferric iron in theelectrolyte in the cell shall not'exceed 2.5%of theiron content, reconcentrating the effluent electrolyte with iron or ironcompound soluble in ferric salt so that the ferric iron shall not exceed.5 gram per litre, and returning the electrolyte to the cell.

3. The process of producing seamless iron tubes consisting incontinuously circulating a substantially saturated hot solution offerrous salt containing a trace of ferric salt in an electrolytic cellin which is rotatably and removably mounted between insoluble anodes acathode capacitated to currents of high density, depositing a partingplane on said cathode, depositing a film of iron on said parting planeby a current of low density, depositing iron upon said film by a currentof high density, controlling therate of circulation in proportion to thedensity of the current so that the ferric iron in the electrolyte in thecell shall not exceed 2.5% of the iron content, reconcentrating theeflluent electrolyte with iron or iron compounds soluble in ferric saltso that the ferric iron shall not exceed .5 gram per litre, andreturning the electrolyte to the cell.

4. The process of depositing seamless iron tubes on a rotatable cathodein a one compartment electrolytic cell which consists in depositing aparting plane on said cathode,

continuously circulating a substantially saturated hot solution offerrous salt containing a trace of ferric salt, electrolyticallydepositing a film of iron on said parting,plane at low current density,rotating said pretreated cathode in the electrolyte before theapplication of current, electrolytically depositing iron upon said filmby \a current of high density, controlling the rate of circulation ofthe electrolyte in proportion to the density of the current supplied tothe anodes so that the ferric iron in the electrolyte in the cell shallnot exceed 2.5% of the iron content, treating the eflluent electrolytein a leaching tank with iron soluble in ferric salt to reconcentrate ituntil the content of iron in ferric form is below .5 gram per litreadjusting temperature to above C., and returning the restoredelectrolyte to the cell.

5'. The process for the industrial manufacture of electrolytic ironwhich consists in preparing an electrolytic solution of soluble ferroussalts, said solution being substantial 1y free from ferrous hydroxideandcontaining ferric iron inan amount not exceeding 2 of the total ironcontent and not less than 0.5 gram per liter of the bath, electrolyzingsaid solution by means of insoluble electrodes, and circulating saidsolution around and past said electrodes at a relatively high speed.

In testimony whereof, I have hereunto set my hand.

GEORGE PRESCOTT FULLER. In testimony whereof, I have hereunto set myhand.

CEDRIC A. VINCENT DAVISS.

